Sunday, November 02, 2014

Ad Ignorantiam and the Law

In a criminal case the probative bar is set very high: the accused has to be shown guilty beyond a reasonable doubt. Here too there seems to be a legitimate appeal to ignorance: if it has not been shown that the defendant is guilty beyond a reasonable doubt, the conclusion to be drawn is that he is not guilty.

We will have to examine this more carefully in a separate post.

Herewith, the separate post. Plainly, the following is an invalid argument:

1. It was not proven beyond a reasonable doubt that it was Smith who killed Jones.

ergo

2. Smith did not kill Jones.

Examples like this appear to support the idea that some appeals to ignorance (or arguments from ignorance) are reasonable and non-fallacious. According to Douglas N. Walton,

. . . the criminal law presumes that a person is not guilty if he has not been shown to be guilty. This is an ad ignorantiam form of argument, but it can be reasonable in the context of the rules of argument in the criminal law. (Informal Logic: A Handbook for Critical Argumentation, Cambridge UP, 2007, 20th ed., p. 47)

I wonder if this is right. Which better represents a criminal process that terminates in an acquittal? Is it the above argument or the following argument?

1. It was not proven beyond a reasonable doubt that it was Smith who killed Jones.

ergo

3. The presumption of Jones' innocence has not been defeated and Jones is in the eyes of the law not guilty.

I now think it is the second argument. But note that (i) the second argument is valid, and (ii) there is no appeal to ignorance in the second argument. The validity of the second, enthymematic, argument is obvious when we make explicit the tacit assumption, namely, that

4. If the accused in a criminal proceeding has not been proven to be guilty of the crime with which he is charged beyond a reasonable doubt, then the presumption of innocence has not been defeated and the accused is in the eyes of the law not guilty.

So the second argument is (formally) valid. It also does not represent an appeal to ignorance. One is not arguing that: Jones is not guilty in reality (as opposed to in the eyes of the law) because it has not been proven that he is not guilty. One is arguing that the presumption of innocence has not been defeated. The following are different propositions:

a. Jones is not guilty

b. Jones' presumption of innocence (POI) has not been defeated.

It ought to be obvious that they are different. They are logically independent. Each is consistent with the negation of the other. Thus the following sets are consistent dyads: {Jones is guilty; Jones' POI has not been defeated}, {Jones is not guilty; Jones' POI has been defeated}.

Conclusion

According to Walton, ". . . the criminal law presumes that a person is not guilty if he has not been shown to be guilty. This is an ad ignorantiam form of argument . . ." I think this betrays a misunderstanding of the notion of presumption, and in particular, presumption of innocence.

The presumption is not that a person is not guilty if he has not be shown to be guilty; the presumption is that he is to be treated as if not guilty, if he has not been shown to be guilty. In the case of O. J. Simpson, almost everyone agrees that he is guilty of murdering Nicole Brown Simpson and Ronald Goldman. Yet he was found not guilty. Obviously, there is a difference between being not guilty (being not guilty in fact) and being found not guilty (being not guilty in the eyes of the law). The presumption of innocence was not defeated in that trial. But that is consistent, as I argued above, with the accused's being guilty.

It is therefore a mistake to think that the POI procedural rule embodies an appeal to ignorance. And since there is no appeal to ignorance here, there is no reasonable or non-fallacious appeal to ignorance.

UPDATE: Dave Bagwill writes,

My grand-dad did not mince words, nor did he suffer fools. When I tried to trick him with verbal technicalities, he would accuse me of "trying to pick the fly shit out of the pepper".

He would have said that about your latest post 'On Ad Ignorantiam and the Law', but he would have been wrong. You made some very fine, fine distinctions in that post that really cut to the heart of the matter. Thanks, and well done. (I've used that book by Walton for years and generally found it useful.)

You're welcome, Dave. My response to your grandfather would be to make yet another distinction, one between hairsplitting and the drawing of necessary distinctions, and then distinguish different kinds of hairsplitting.

One sort of hairsplitting is to make distinctions that correspond to nothing real, distinctions that are merely verbal. The 'distinction' between a glow bug and a fire fly, for example, is merely verbal: there is no distinction in reality. A glow bug just is a firefly. Similarly there is no distinction in reality between a bottle's being half-full and being half-empty. The only possible difference is in the attitude of someone, a drunk perhaps, who is elated at the bottle's being half-full and depressed at its being half-empty.

But this is not what people usually mean by the charge of hairsplitting. What they seem to mean is the drawing of distinctions that don't make a practical difference. But whether a distinction makes a practical difference depends on the context and on one's purposes. The truth of the matter is that there are very few occasions on which the charge of hairsplitting is justly made. On almost all occasions, the accuser is simply advertising his inability to grasp a distinction that the subject-matter requires.

Walton may be the premier writer on informal logic. His book is apparently well-thought-of. 2007 saw the 20th edition. I'd guess there have been editions since then.